Object Oriented Programming

1
Object Oriented Programming

• Irfan Pyarali
• http//www.cs.wustl.edu/irfan/cst310/Lecture2.ppt

2
Object Orientation Real or hype

• A little of both
• False claims and misinformation have led to
• confused consumers
• mistrust of object-oriented technology

3
Characteristics of OOP

• Encapsulation
• to gather data representation and behavior into
  one entity
• has interface and implementation
• Inheritance
• derive a new data type from an existing one
• reuse, don't reinvent.
• Polymorphism
• customize the behavior of an object

4
What is an object?

• An object is a software bundle of variables and
  related methods
• Real-world objects
• a dog, a desk, a television set, a bicycle
• Objects have
• state
• behavior

5
What is a class?

• Many objects of the same kind
• A class is a blueprint or prototype that defines
  the variables and methods common to all objects
  of a certain kind.

6
Objects versus classes

• Objects are instances of classes
• a blueprint of a bicycle is not a bicycle

7
What are messages?

• Software objects interact and communicate with
  each other using messages.
• A single object alone is generally not very
  useful
• Usually appears as a component of a larger
  program
• Through the interaction of these objects,
  programmers achieve
• higher order functionality
• more complex behavior

8
Message composition

• Three components of a message
• The object to whom the message is addressed
• The name of the method to perform
• Any parameters needed by the method

9
Inheritance

• A class inherits state and behavior from its
  superclass.
• Subclasses provide specialized behaviors from the
  basis of common elements provided by the
  superclass.
• Code reuse